The outermost layer of a printed wiring board generally has a solder resist layer in order to protect a conductor circuit. When a solder bump is to be formed, a solder pad is formed by opening part of the solder resist such that the interior is exposed in order to connect to the conductor circuit. After a nickel layer and a gold layer have been applied onto a section that is to become a solder pad solder paste is printed thereon and reflow operation is performed so as to form the solder bump. The solder layer is formed at a portion that connects with an external board, and an externally connecting terminal is disposed. As prior art, JP 10-154876 A has been proposed.